The use of various coagulants for the flocculation of suspended solids from aqueous solutions is well known in the art. Many coagulants are known including alum, aluminum sulfate, ferric chloride, ferric sulfate and lime. Commonly used polyelectrolytes for this purpose include polydimethyl (p-DMDAAC) and Epi-DMA polyamine.
Blends of the inorganic coagulants with polyelectrolytes are known in the art. These blends combine the desirable properties of each component in the system to be treated without the need of feeding two separate additives at different points in the system. This presents a cost advantage in many circumstances and greatly simplifies treatment for many systems.
U.S. Pat. No. 5,035,808, the disclosure of which is incorporated herein in its entirety by reference, teaches the blending of commercial grade solutions of ferric salts and cationic polymers. Commercial grade ferric sulfate solution can be blended with either polyamine or p-DMDAAC to form stable products. However, it was not possible to prepare a viable product by blending commercial grade ferric chloride solutions (38-42 wt % active raw material) with p-DMDAAC. Such a blend was not possible because a gel would be formed immediately upon mixing. This problem is noted in column 3, lines 3-6 of U.S. Pat. No. 5,035,808. Instead, it was only possible to blend commercial grade ferric chloride solutions with polyamine.
Each group of polyelectrolyte has its own set of unique properties that it brings to the blend of polymer and inorganic coagulant. It would be very desirable to be able to combine the benefits of ferric chloride with those of p-DMDAAC in a composition that could be added as a single component to treat water systems.